It has long been common practice in the manufacture of mass produced parts, such for example, as carburetor housings, automatic transmission housings, cylinder blocks and the like, to mount the part on a pallet, fixture or a jig and, while so mounted, move the part through a number of work stations. At each work station one or more machining operations are performed and the part is then transported to another work station where additional machining operations are also performed. The parts mounted on their pallets, fixtures or jigs are transported from work station to work station on conveyors and remain on the conveyor or a spur track of the conveyor at each work station. This arrangement has a number of drawbacks and limitations.
In our earlier application, we disclosed a system and a work piece holding cuboidal jig which is so designed that the workpiece will be positioned at each work station with a known reference point by which it can be automatically and quickly positioned accurately, with respect to the tool that is to work on it. While this system has proven itself to be capable of dependable repeatable accuracy not previously attained by any system, it did have the drawback that the fixtures frequently could not be reused when the production run of a particular type of part was over. Since the fixtures are relatively expensive, this represented a tooling cost which it would be desirable to reduce. Further, the ease and the speed with which one of the cuboidal fixtures can be prepared to properly support a workpiece would be improved if the interior of the fixture could be made more accessible without either adversely affecting the accuracy of the fixture or its strength to withstand the pressures and distortion creating loadings which are imposed upon these types of fixtures by the operation of the work cells at the machining stations and by the tools used to perform the machining functions. Particularly, is the latter a problem in modern machine shop practice because, to increase productivity, the rate at which machining operations are carried out has been materially increased, necessitating exertion of greater and greater tool pressure on the workpiece.